Dell does not upgrade computers, they only sell new ones.
You may not be able to reuse the ram, depending on what ram you have and what motherboard you choose - and you cannot reuse the floppy drive because it has no bezel.
My advice? Start saving for a new computer, and build one yourself this time. Sell the Dell to someone who needs a reliable office machine and doesn't care about games. That's all those entry level Dells are good for anyway - general nondemanding use.